zachariassen



Feb. 1956 s. H. B. ZACHARlASS-EN 2,733,725

DOSING METHOD AND DEVICE Filed Feb. 10, 1950 2 Sheets-Sheet 1 i i i i iINVENTOR.

.Sf/g Ho/ger B brneZachar/bssn BY 19% wa W e 7, 1956 s. H. B.ZACHARIASSEN 2,733,725

DOSING METHOD AND DEVICE Filed Feb. 10, 1950 2 Sheets-Sheet 2 JNVEN TOR.529: Ho/ger Bjorne Zbc/van'axn United States Patent nosING METHOD ANDDEVICE Stig H. Bjarne Zachariassen, Stockholm, Sweden, assignor toAktiebolaget Separator, Stockholm, Sweden, a corporation of SwedenApplication February 10, 1950, Serial No. 143,379

7 Claims. (Cl. 137-42) This invention relates to dosage devices forcontinuously mixing a certain quantity of one liquid with anotherliquid.

There are numerous processes in which a liquid, often in a smallquantity, must be continuously mixed with with another liquid. This iscalled dosage and is usually carried out so that a continuous stream ofthe dosage medium is fed into a continuous stream of the other liquid.Thus, lye, for example, is mixed with vegetable oil to refine thelatter. As the mixture. of the liquids often takes place atsuper-atmospheric pressure, a pump is required to force the dosagemedium into the other liquid. This pump must fulfill certain conditionswhich do not apply for ordinary pumps. Thus, the pump should not befitted with a stufiing box, because generally the dosage liquid iscorrosive and will damage the packing material. Furthermore, the pumpmust be able to exert a comparatively high pressure. It should alsodeliver liquid at a rate whch is practically constant but capable ofregulation within wide limits independently of the counter-pressure. thepump must, on the other hand, be limited so that the pressure does notrise too much if the pressure pipe should become clogged. For thisreason pumps of cog or screw type are unsuitable. Neither centrifugalnor gear pumps fulfill these requirements.

It is an object of the present invention to provide an improved dosagedevice which will meet these requirements.

According to the present invention, the problem is solved by the use ofa pump with a rotating housing for the dosage, the liquid being expelledfrom this housing by means of a paring disc or other paring device whichextends into the body of the rotating liquid. The liquid is led into thepump housing through a central channel and is then made to rotate withthe pump housing by a vane or other suitable conveyor device. At first,the liquid forms a layer in the outer part of the pump housing. Then, asmore liquid is passed into the pump housing, the free liquid level isdisplaced inward until it reaches the paring device which catches theliquid and leads it out of the pump through a discharge pipe. When acounter-pressure must be overcome, the liquid in the rotating pumphousing must cover the paring device to a larger extent so that thepressure in the discharge channels is suflicient. The coverage isincreased and the liquid level is thus displaced inward toward the axisof rotation until a pressure sufiicient to overcome the counter-pres-,sure has been reached. The pump now conveys the liquid via thedischarge pipe into the other stream of liquid without changing theliquid level in the pump housing. Should the pressure in the pipe of theother the housing, and with falling counter-pressure the liquid Themaximum pressure exerted by level is displaced outward.

The pump is thus capable of adapting itself to the changes incounter-pressure immediately. V I

The capacity of the pump is regulated in advance of the pump. As theliquid pressure at the inlet side of the pump can be kept very low,comparatively simple devices can be used for the adjustment and controlof the capacity. Due to the low pressure there is no risk of themeasuring instruments bursting. Pipediameters and through-flow areas invalves can be kept large enough to prevent clogging. When regulation ofthe quantity of dosage liquid is effected on the pump outlet or pressureside, the pressure must be kept very high, so that the variations inpressure in the dosage liquid do not greatly influence the dosage, i. e.the quantity of dosage medium added. This requires very small valveopenings and other flow-channels, which may cause clogging' If gear orscrew pumps are used for the dosage, there will be an unlimited pressurerise during clogging, which may easily burst the measuring instruments.This risk is entirely eliminated when using a pump with a rotatinghousing, and the capacity is independent of the counter-pressure withinsatisfactory limits. Centrifugal pumps do not provide this protection.

During changes in the counter-pressure, the liquid level in the pumphousing is displaced, as already mentioned, around the paring device.This causes a momentary increase or reduction of the quantity of dosagemedium forced in per unit of time. As soon as the liquid level in thepump housing has reached a position corresponding to the new pressure,the throughput becomes normal again. In order to minimize thedisturbance in capacity, the volume of liquid in the pump between thetwo levels should be as small as possible. The paring device should,therefore, be adapted to the pump housing with a minimum of play.

To regulate the capacity of the pump, i. e. the quantity of dosagemedium conveyed by it per unit of time, it is preferable to use aregulating device operating at atmospheric or any other low pressure.The dosage medium can thus be kept in an open vessel or in a vessel atatmospheric or any other low pressure, the vessel being fitted with acontrollable dischargepipe extending into a space under atmosphericpressure or the deviating pressure prevailing in the vessel. To regulatethe capacity, a simple valve can be mounted on the discharge pipe. Thislast pipe may extend directly into the central part of the rotating pumphousing. Alternatively, it may extend into a tank arranged in advance ofthe pump, thetank being connected to the pump housing and provided witha float valve which maintains a constant liquid level in the tankindependent of the capacity. 1

As an alternative, the regulation may also be efiected by means of adosing device capable of more accurate regulation and having the form ofa vessel provided with a vertically adjustable level overflow for excessliquid to be returned and with an outlet for the dosing liquid,

which outlet is at a lower level and also capable of regulation. Theliquid, the amount of which per unit of time is thus accurately fixed,is preferably fed to the inlet of the pump through a quantity meter inorder to control the amount fixed.

For a better understanding of the invention, reference may be had to theaccompanying drawings, in which- Fig. l is a vertical sectional view ofone embodiment of the invention, showing a dosage device with a simplevalve placed in the outlet pipe of the vessel containing the dosageliquid, and

Fig. 2 is a similar view of another embodiment of the invention, showinga dosage device of a different type and also a quantity meter forcontrolling the dosing.

In pipe 1 there is a flow, under pressure, of a liquid,

l atented Feb. 7, 1956 were a pipe 2 connected to a dosage pump having apump hous- The dosage medium is delivered via the pumpffronja P p-6.:fitted with..a. eul t i5 n a in to a cup 7-.pro vided;with a:float8. Thellatter is moyable vertically;alolngj.an upright 9genc losing achannel 10;exten ding into ,the lowenpart of the pump housing 3. Thefloat has1a;sleeive11 surroundingtheupright 9, to cover the inlet,opening'12 of the channellO. By means of the float, a constant liquidlevel'is'maintained inthe cup 7 so that airi'sprevented fromentering thechannel 10 and into pump housing 3. Below the outlet end of channel 10is a conveyor 13,;suchas a vane or wing rotating with the pump-housingand expelling theliquid through radial channels 14. into the outer partof the pump housing. The liquid-finds its way aroundtthe paring disc4-to a free liquid, leyel 115,: which represents an equilibrium positionat which the, liquidis forced .into the paring disc at a pressurecorrespondingto the pressure in pipe 1. From theinflow. channels 1610fthe paring disc,'the liquid is conductedthrougha system of channels 17between the upright 9 :and' the surrounding neck/ta of the parer, topipe Z'and intojpipe 1.

To prevent air from getting into the paring disc at a smallcounter-pressure, when there is a small amount of liquid cover'ingthedisc, the latter may be provided with radial flanges: 26 extendingoutwardlysomewhat beyond theinlet openings of the paring disc.

The pump housing-'3 isfixed on' a spindle 18 supported ina frame 19'and'driven by a power source (not shown). The pump housing is formed sothat its bottom part 20 can be'separated from its top part 21 byloosening a ring nutf22.- Between these housing parts is a packing 23.The frame 19 -isp'rovided with a cover 24 wherein the upright 9,- whichsupports the cup 7 and the paring disc 4, is mounted by mea'ns of afixture 25. t

It isimportantthat the free liquid surfaces, formed at the level 15, areas small-as possible. The play or radial clearance between the paringdisc 4 and the pump housing should therefore be comparatively small. Onthe other hand, that part-of the pump housing which is situated outsidethe paring disc should-be spacious and form a large sludge'space.From'this-standpoint, the design asillustrated'is favorable, because thedistance between the cover "21 and the bottom part of the pump housingis comparatively large. The channel 14 is enclosed in a part whichextends as far as the vicinity of the paring disc 4 but leavesthe sludgespace free. In place of the part referred to above, the bottom part ofThe dosing device 27 comprises afloat-actuated valve 31, arranged tokeep in thlefievice aliquid level 33, adjustable by means of the screw32. The dosage liquid thus flows through the needle valve 34 at a fullyfixed pressure into pipe 28. When it is desired to increase the amountof dosage liquidper unitof time, the screw 32 is turned to the right, sothat a part 35 holding the screw 32 is raised and.w ith it'the shaft 36on which the float 37 the'purnp housing immediately in'front of thelevel 15 can be widened in an upward-direction'to a corresponding degreeand enclose the channel 14.-

It'willbe understood that the valve 5 constitutes a means for regulatingthe rate of flow of the dosage medium through pipe 6, and therefore therate at which the dosage medium is conveyed to pipe 1. The vessel 5::supplying the pipe 5 is under the same pressure as the space in thecentral part of the rotary housing 3. Thus, ifthe supply vessel 5a is atatmospheric pressure, as inthe'preferred case,'*the"central space in thehousing 3 is likewise' at atmospheric pressure, by reason of 'itscommunication with atmosphere through the annular vent opening 3abetween'the neck 4a of the parer and the surrounding part of the cover21; V

In Fig. 2 I have shown a modified regulating device for the supply ofdosage agent to the pump, By adjusting a dosing device 27, the amount ofdosage agent supplied per unit of time is determined; This devicecommunicates through a pipe 28 wi'th' a quantity or' flow meter 29Which,]in turn, is connected to the part 25a throu'gh a pipe 30'; Thedosage fixed-by the device;27-is read on the.meter29;

swings. The valve 31 is thereby opened until equilibrium is reached at ahigher level, with higher liquid pressure at the port 34 andconsequently alarger quantity of liquid. As an alternative, theregulation may be efiected by means of the needle :valve 34pand thescrew 32 may then be dispensed with.

It will be understood that through the present invention the dosing of astream of one liquid with a stream of a second liquid is efiected by amethod in which the pressure of the second or dosing liquidstream isautomatically adjusted in accordance with pressure variations in thestream of liquid to be dosed. More particularly, the second liquid is,fed at, a rate controlled by valve 5 to the locus of centrifugal forcein-the rotary housing 3, Where the centrifugaljforce maintains thisliquid in an annulus againstthe peripheral wall of the housing. By meansof the stationary paring disc 4, liquid is pared from a fixed point ofthis locus at. thev inner portion of the liquidannulus, since the disc 4extends outwardly into this annulus from the rotationraxis of housing 3.The liquid thus paredfiows from this fixed point through the confinedpath formed by channels 17 and pipe 2 to the merging zone at the.junction of pipes 2 and 1, this flow being under. the pressure generatedby the action of the centrifugal force on .the liquid annulus in housing3. The liquiditobe dosedis forced through this merging zone in theconfined pathaformed by pipe 1 at a substantially constant rate (asisthe practice in the use of dosing devices), this rate being independentof the liquid flow through pipe 2.v However, the pressurein pipe 1 mayvary from time to time. due .to changes in the counterpressure againstwhich the liquid to .be dosed is fed, as previously mentioned.

Assuming that the dosage device is in a state of equilibrium, it will beunderstood'that when the pressure in pipe 1 is increased; the pressuredifference between the inlet orifice of'each paringchannel 16 openinginto the centrifugal locus of the rotating housing 3 and the dischargeorifice of the pipe 2 opening into the pipe 1 is reduced. As a resultof-this, the throughput rate in the paring device is decreased. Sincethe rate of supply of liquid to therotating housing 3 through pipe 10 iskept constant, there will thus be an accumulation of liquid in therotating housing, and this accumulation necessarily results in the level15of the liquid annulusmoving inwardly towardthe rotation axis so thatthis level of the inner portion of the liquid annulus automaticallyincreases relative to the paring disc 4.; The level difference betweenthe new liquidalevel 15 "and the prior one corresponding to theequilibrium state represents a certain pressure which is added'to thepressure which prevailed at the inlet of each; channel 16-during theaforementioned state of equilibrium. Consequently,'the throughput ratein the channels 16 and the paring device will increase, until a newequilibrium stat eis reached.

1. A dosage device comprisinga pipe for the dosage medium, means"communicatingWith -said pipe for regulating the rate of flow of thedosage medium therethrough, a rotary housing for receiving the do sagemedium from the pipe, whereby the dosage medium forms ,a whirlingannulus inthe peripheral part of the housing, the housing having a ventopening communicating with'the space within said annulus, a stationaryparing device disposed in the'housing-and operable'to-pareliquidfromsaid annulus, a second 'pipe-in which the liquid to be mixed with thedosage medium flows under varying pressure-at a substantially constantrate independent of the flow through the hereinafter specified flowconnection, and a closed flow connection between the paring device andsaid second pipe.

2. A dosage device according to claim 1, comprising also a vessel forsupplying the dosage medium to said first pipe, the rotary housinghaving a central space at substantially the same pressure as said vesseland communieating therewith through said first'pipe.

3. A dosage device according to claim 1, comprising also a vessel forsupplying the dosage medium to said first pipe, the rotary housinghaving a central space at substantially the same pressure as said vesseland communicating therewith through said first pipe, said space andvessel being under atmospheric pressure.

4. A dosage device according to claim 1, comprising also a stationaryframe supporting the housing for rotation, an upright mounted on theframe and supporting at its lower end the paring device, the uprighthaving an inlet channel for the dosage medium leading to the interior ofthe housing, a tank mounted on the upper end of the upright and throughwhich the dosage medium is fed from said first pipe to the inletchannel, and a float in.

the tank for throttling the flow of said medium to the inlet channel tomaintain a minimum liquid level in the tank.

5. A dosage device according to claim 1, comprising alsoa flow meterconnected to said first pipe for indicating the rate of flow of thedosage medium as regulated by said means.

6. In combination with a pipe through which a liquid flows under varyingpressure at a substantially constant rate, a device for feeding anotherliquid into said pipe at a substantially constant but regulatable rateirrespective of variations in said pressure, comprising a second pipefor conveying said other liquid, means communicating with said secondpipe for regulating the fiow rate therethrough, a rotary housing forreceiving the liquid from the second pipe, said last liquid forming awhirling annulus in the peripheral part of the housing, the housinghaving a vent opening communicating with the space within said annulus,a stationary paring device disposed in the housing and operable to pareliquid from said annulus, and a closed flow connection between theparing device and the first pipe, whereby said variations are operablethrough said flow connection to change the liquid level of said annulusrelative to the paring device and thereby counteract said variations intheir effect upon the rate of feed of said other liquid into the firstpipe.

7. 'In the dosing of one liquid with a second liquid by merging separatestreams of the respective liquids in a merging zone, the method whichcomprises feeding said second liquid at a controlled rate to a locus ofcentrifugal force, maintaining a variable annulus of the second liquidin said locus by centrifugal force, paring liquid from a fixed point ofsaid locus at an inner portion of said annulus, flowing the pared liquidfrom said fixed point through a first confined path to said zone underpressure generated by the action of the centrifugal force on saidannulus, and flowing said first liquid in a second confined path throughsaid merging zone at a substantially constant rate independent of theliquid flow through said first confined path and against a varyingpressure, whereby an increase in said last pressure automaticallyincreases the pared liquid pressure in said first path by increasing thelevel of said inner portion of the annulus relative to said fixed point.

References Cited in the file of this patent UNITED STATES PATENTS France1943

